1. Field of the Invention
This invention relates generally to laminar flow wings and deicing devices for aircraft, and relates more particularly to a movable sheet that serves as a renewable, laminar flow suction surface, and alternatively as an integral, retractable shield for protecting a suction support structure of a wing against contamination, and that also serves as a movable, conductive substrate for deicing by means of electrical resistance or hot-gas heating and substrate movement. Furthermore, the movable sheet serves to protect the wing surface from debris impact damage and corrosion.
2. Description of the Relevant Art
Laminar flow wings have been proposed in order to reduce drag in aircraft. Laminar flow concepts include shaping the airfoil to enhance laminar flow for small wings, and active measures such as boundary layer suction for larger wings. Promoting laminar flow through suction operates on the principle of removing low energy air from the boundary layer to delay the transition from laminar to turbulent or separated flow.
A suction device for a laminar flow wing typically has a suction support structure comprising a perforated, slotted, or otherwise porous skin on the upper and/or lower surface of the wing. Boundary layer air is sucked through the suction support structure and into a vacuum plenum or manifold located within the wing. A problem that arises with such a suction device is that insects, airborne debris and ice can clog the perforations or slots in the suction support structure and thereby degrade the performance of the suction device. This problem is of concern at low and medium altitudes. Prior to the present invention, large laminar flow wings have been impractical for commercial use in part because of the difficulty in keeping clear the tiny perforations.
Another design consideration for aircraft is the need to prevent ice from accumulating on a wing. Deicing concepts include using chemicals to retard ice formation, using an inflatable or deformable wing surface to break the ice, and heating the wing surface to melt the ice and/or the interface between the ice and the wing. Presently, the chemicals used for wing deicing are toxic and cause great environmental damage. Wing heating requires large amounts of energy, and is heavy and costly. The present invention alleviates these problems.